1. Field of the Invention
The present invention relates to a pixel structure of a transflective liquid crystal panel, and more particularly, to a pixel structure of a transflective liquid crystal panel having a single cell gap.
2. Description of the Prior Art
Most liquid crystal displays (LCDs) can be categorized into the transmissive type, the reflective type, and the transflective type. The transmissive liquid crystal display uses backlight as a source for emitting light. The light emitted by the backlight will pass through the liquid crystal panel to let an observer see the image displayed on the liquid crystal display panel. The reflective liquid crystal display has a reflective electrode. When displaying the image, the ambient light of the reflective liquid crystal display will enter the liquid crystal display from the observer side of the liquid crystal display and then be reflected by the reflective electrode. The reflected light will pass through the liquid crystal panel again, and finally the observer can see the image displayed on the liquid crystal display. The transflective liquid crystal display has the liquid crystal display both of transmissive type and reflective type. In other words, each pixel region of the liquid crystal panel comprises a transmission region and a reflection region, wherein the transmission region uses a backlight, and the reflection region uses an ambient light as a light source.
Referring to FIG. 1, which is a schematic diagram of a traditional transflective liquid crystal panel. As shown in FIG. 1, traditional transflective liquid crystal panel 10 comprises an array substrate 20, a color filter substrate 30, and a liquid crystal layer 40 disposed between the array substrate 20 and the color filter substrate 30. The array substrate 20 comprises a plurality of pixel regions 22, and each of the pixel regions 22 comprises a reflection region 221 and a transmission region 222. The array substrate 20 also comprises a plurality of thin-film transistors 23, each thin-film transistor 23 disposed in each reflection region 221, a plurality of reflective electrodes 24 disposed on the thin-film transistors 23, and a plurality of transmissive electrodes 25 disposed in the transmission regions 222. Both of each reflective electrode 24 and each transmissive electrode 25 are electrically connected to each thin-film transistor 23 and controllably driven by each thin-film transistor 23. In addition, there is also a dielectric layer 26 disposed between the reflective electrode 24 and the thin-film transistor 23, and the dielectric layer 26 has a rough surface, so that the reflective electrode 24 can have a rough surface for scattering light beams.
The color filter substrate 30 comprises a plurality of color filters 32 disposed corresponding to the pixel region 22 and a black matrix 34 disposed corresponding to the edge of each pixel region 22.
Because the transmission region 222 of the transflective liquid crystal panel 10 uses a backlight, the light will pass through the liquid crystal layer 40 only once. The reflection region 221 uses the ambient light as a light source, so that the light will pass through the liquid crystal layer 40 twice. In such a case, because the phase difference in the reflection region 221 is twice as big as that in the transmission region 222, the relation of reflectance versus voltage mismatches the relation of transmittance versus voltage while driving the liquid crystal molecules. For this reason, the traditional transflective liquid crystal panel 10 uses a design of a double cell gap to solve the mismatching problem. More specifically, in the traditional transflective liquid crystal panel 10, a function of the dielectric layer 26 is disposed under the reflective electrode 24 so as to adjust a cell gap of the liquid crystal layer 40. By disposing the dielectric layer 26, the cell gap of the liquid crystal layer 40 in the reflection region 221 is smaller than the cell gap in the transmission region 222, so that the phase difference of light passing through the reflection region 221 is the same with that of light passing through the transmission region 222. Then, the mismatched problem of driving voltages in the reflection region 221 and in the transmission region 222 is improved. However, a step of fabricating the dielectric layer 26 in the reflection region 221 has to be increased in the double cell gap design of the transflective liquid crystal panel 10. Further, the increased step not only increases process time and cost, but also affects product yield. Importantly, a gap of the border between the reflection region 221 and the transmission region 222 will make the liquid crystal molecules difficult to align, thereby lowering the quality of displayed images.